About hollow core doors: Do they need some reinforcement or are they sagproof? I have one but before I use it can it be made as nearly flat as possible with this type of material. At this time I am using a 25"X49" piece of 1 1/2 thick particle board with a laminate surface I picked up where I work. I just checked and discovered ther is a slight bow enough to easily slide a sheet of copier paper under a straight edge. The gap is close to .5mm. I am going to hardware to locate some angle steel or aluminum to reinforce the bottom of the sheet in hopes of bringing the surface true. jollyroger